t1304: improve setfacl prerequisite setup

t1304: improve setfacl prerequisite setup

t1304 first runs setfacl as an experiment to see whether the
filesystem supports ACLs, and skips the remaining tests if
it does not. However, our setfacl run did not exercise the
ACLs very well, and some filesystems may support our initial
setfacl, but not the rest of the test.

In particular, some versions of ecryptfs will erroneously
apply the umask on top of an inherited directory ACL,
causing our tests to fail. Let's be more careful and make
sure both that we can read back the user ACL we set, and
that the inherited ACL is propagated correctly. The latter
catches the ecryptfs bug, but may also catch other bugs
(e.g., an implementation which does not handle inherited
ACLs at all).

Since we're making the setup more complex, let's move it
into its own test. This will hide the output for us unless
the user wants to run "-v" to see it (and we don't need to
bother printing anything about setfacl failing; the
remaining tests will properly print "skip" due to the
missing prerequisite).

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>